Law enforcement agencies in the US had been suspicious of financier and cricket mogul Sir Allen Stanford's activities for 15 years, an expert on international fraud called Jeffrey Robinson has claimed.

Journalist Mr Robinson said Sir Allen who is being sought by the US Securities and Exchange Commission after being charged with a multi-billion dollar fraud, had been on "everybody's radar".

Mr Robinson also said the Stanford case could have "huge ramifications" for the world of offshore banking.

He said: "I know, personally, because I have discussed it with them, a number of law enforcement agencies in the United States, plus a number of prosecutors who have been looking at Mr Stanford for the past 15 years.

"He has been on everybody's radar for a number of things."

Some people involved in the offshore industry would be keen for Sir Allen to remain silent about his Antiguan-based banking empire, Mr Robinson told BBC Radio 4's Today programme: "Now, innocent until proven guilty? Yes. Guilt by association? No, I'm not insinuating that."

He added: "What's going to happen now is they will ask to talk to him. If he doesn't appear, I suspect an arrest warrant will be issued by the FBI on criminal charges.

"If he does, he's got a real problem because he knows an awful lot. And I would suspect there are a number of people, very heavyweight people, throughout the offshore world and in other jurisdictions who really don't want to be associated with Mr Stanford and are not going to be pleased if he talks.

"So this man has a very, very serious problem."

He said the Stanford case could be as significant as the investigation into the massive fraud allegedly committed by US financier Bernard Madoff.

Mr Robinson said: "This is going to be as major as the Madoff affair, perhaps not in the volume of money but in the noise it makes.

"It will have huge ramifications to the offshore world."

The Texas-born tycoon was unlikely to get protection from the authorities in Antigua, where the Stanford Investment Bank is based, Mr Robinson predicted.

Sir Allen created both the largest offshore bank and the largest onshore banks on the Caribbean island, Mr Robinson said.

The scandal surrounding the businessman has led to a run on his Bank of Antigua as anxious Antiguans sought to withdraw their savings.

Mr Robinson said: "When you get a banking licence in the offshore world, one of the rules is don't hurt the locals, don't hurt the natives.

"His onshore bank has now hurt the Antiguans, there are a lot of people who are losing money.

"I think what we are going to see is that the Government of Antigua will not protect him and that an awful lot of things will now come out."